Recently I reviewed a client's query letter. It was a hard working query letter, detailing the marketing prospects for the book, her own glowing credentials and the contacts she possessed that would help her publicize the book. But she left out one teeny weeny thing: she didn't say what her book was about! I used to think query letters were relatively easy, but now I realize that a query has to do so many things that it's easy to forget essential elements. Since the letter is your first step in putting your book's best foot forward, you don't want that to happen. So here's a simple rundown on what goes into a solid query letter.
Who Are You?
It's tempting to start the letter by leaping into a breathless description of what you're sure is going to be the best book in the world, but resist a little longer.

You want to use your first paragraph to introduce yourself and let the agent know why he or she should pay attention to you. Tell the agent who you are. Describe your qualifications, including a bit about your current activities which will in turn describe your platform. Have you been doing speaking engagements? Do you appear on television? Are you noted in your profession? Have you won any awards? Do people look to you as an expert in your subject? Do you teach? For instance, if you are a workshop or seminar leader in real estate finance, frequently travel across the country, and have 5,000 people attending your workshops every month, you can tell the agent:"Now I’ve decided to give away all of my secrets in a book about real estate financing with no money down." Anything that puts you in front of people is a potential place to sell your book so don't forget to mention such activities.

What's Your Book About?
In the next two or three paragraphs of the letter you get to talk about your wonderful book idea and/or story. As a guideline, it may help you to read the backs of book covers. You'll want to do something similar--a brief synopsis of your book with enough spark it will intrigue the agent or any other potential reader, to pick up your book. Use bullet points to highlight what amazing tidbits the reader will get out of the book. Will they get five strategies on how to eat without gaining weight? Or 4 low cost resources for financing a large home improvement project? Or the 6 surefire signs you've found your life purpose? Make this description tight, concise and, of course, hugely interesting. Then you can move on to.
Your Great Marketing Plan--With You As the Star
The query letter should include a brief paragraph or two about how you're going to market the book. Of course, if you go with a traditional publisher you'll get major help in this area from the publishing house. But remember this: no one will be a better advocate for your book than you. And when editors are considering manuscripts they're also considering what kind of a marketing presence they'll be getting with the author.

You'll make their job easier--and your book much more successful--if you can bring your own marketing plan to the table to work hand in hand with the publisher's. Do you have contacts in the media willing to help? Are you good at getting quoted in newspapers and magazines? Do you publish freelance articles that can mention your upcoming book? Put a lot of thought into this. Too many writers go into the publishing process expecting everything to be done for them and then are disappointed. Having a good marketing plan would show a potential agent that you're serious and you understand the business.
The Next Step
You’ve mentioned your credentials, described your book and your stellar marketing plan. Ideally, at this point, you have the agent intrigued. You want him or her to say, "Great! What does this person have to offer?" This is where your letter would say something like, "I would love for you to see more and I have a proposal" or "I have 50 pages of a manuscript." Whatever you want the agent to see next, offer it up and ask, "May I send this to you?" Asking permission is always a classy thing to do, it shows you're not being presumptuous. Then you move into a closing that let's the agent know you'll follow up in a certain amount of time either via phone or email (they might prefer email).
When you're done, read your query letter over many times.